The STAR Tracking Upgrade

TL;DR

The paper discusses an upgrade to the STAR experiment's tracking system, incorporating new technologies like active pixel sensors and GEM detectors to enhance heavy flavor and W boson measurements in high-multiplicity environments.

Contribution

It introduces a new tracking system design with active pixel sensors and triple GEM disks, optimized for heavy ion and polarized proton collision environments.

Findings

Active pixel sensors tested successfully in STAR.

Triple GEM detectors developed and beam-tested at Fermilab.

Upgrade improves heavy flavor and W boson detection capabilities.

Abstract

The STAR experiment at the Relativistic Heavy Ion Collider RHIC studies the new state of matter produced in relativistic heavy ion collisions and the spin structure of the nucleon in collisions of polarized protons. In order to improve the capabilities for heavy flavor measurements and the reconstruction of charged vector bosons an upgrade of the tracking system both in the central and the forward region is pursued. The challenging environments of high track multiplicity in heavy ion collisions and of high luminosity in polarized proton collisions require the use of new technologies. The proposed inner tracking system, optimized for heavy flavor identification, is using active pixel sensors close to the collision point and silicon strip technology further outward. Charge sign determination for electrons and positrons from the decay of W bosons will be provide by 6 large-area triple GEM disks currently under development. A prototype of the active pixel detectors has been tested in the STAR experiment, and an extensive beam test of triple GEM detectors using GEM foils produced by Tech-Etch of Plymouth, MA has been done at Fermilab.